1. Field of the Invention
The present invention relates to a apparatus for measuring impurities in water, and more particularly to an apparatus for measuring the total amount or level of impurities in water based on the time-dependent change of flow rate of the water passed through a filter.
2. Description of the Prior Art
Conventionally, a direct microscopic method, the FI (Fourier Index) value method (disclosed as the SDI method in Handotai Process Zairyo Jitsumu Binran p. 438 published by Science Forum Company, Apr. 25, 1983, for example), and the like, have been known as methods for evaluating the purity of water. According to the first method, water extracted at an actual supply is filtered through a filter of 0.2 .mu.m hole diameter and the minute particles on the filter are examined with a microscope. According to the second method, a prescribed amount of water is passed through a filter of 0.45 .mu.m hole diameter under a constant pressure and the time for such passage is measured.
It is known that among impurities found in water there are materials of extremely small particle diameter, such as a colloidal material. However, in the above-described direct microscopic method, only minute particles larger than 0.2 .mu.m can be captured, so that the above-described colloidal material can not be measured. In addition, much labor and skill are required in the measurement. In the FI value method, only filters having hole diameters larger than 0.45 .mu.m are used at present in consideration of the time required for filtering. Therefore, only minute particles larger than 0.45 .mu.m can be captured so that amounts of the aformentioned colloidal materials can not be measured.
In addition, neither of the above described methods is capable of continuous monitoring in the field, where water is used, and neither of them can cope with a sudden change in the quality of the water.